1//
2// Copyright (c) Chris Glover, 2016.
3//
4//
5// Distributed under the Boost Software License, Version 1.0. (See accompanying
6// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
7//
8
9#ifndef BOOST_TYPE_INDEX_RUNTIME_CAST_STD_SHARED_PTR_CAST_HPP
10#define BOOST_TYPE_INDEX_RUNTIME_CAST_STD_SHARED_PTR_CAST_HPP
11
12/// \file std_shared_ptr_cast.hpp
13/// \brief Contains the overload of boost::typeindex::runtime_pointer_cast for
14/// std::shared_ptr types.
15
16#include <boost/type_index/runtime_cast/detail/runtime_cast_impl.hpp>
17#include <memory>
18
19#ifdef BOOST_HAS_PRAGMA_ONCE
20# pragma once
21#endif
22
23namespace boost { namespace typeindex {
24
25/// \brief Creates a new instance of std::shared_ptr whose stored pointer is obtained from u's
26/// stored pointer using a runtime_cast.
27///
28/// The new shared_ptr will share ownership with u, except that it is empty if the runtime_cast
29/// performed by runtime_pointer_cast returns a null pointer.
30/// \tparam T The desired target type to return a pointer of.
31/// \tparam U A complete class type of the source instance pointed to from u.
32/// \return If there exists a valid conversion from U* to T*, returns a std::shared_ptr<T>
33/// that points to an address suitably offset from u.
34/// If no such conversion exists, returns std::shared_ptr<T>();
35template<typename T, typename U>
36std::shared_ptr<T> runtime_pointer_cast(std::shared_ptr<U> const& u) {
37 T* value = detail::runtime_cast_impl<T>(u.get(), std::is_base_of<T, U>());
38 if(value)
39 return std::shared_ptr<T>(u, value);
40 return std::shared_ptr<T>();
41}
42
43}} // namespace boost::typeindex
44
45#endif // BOOST_TYPE_INDEX_RUNTIME_CAST_STD_SHARED_PTR_CAST_HPP
46

source code of boost/libs/type_index/include/boost/type_index/runtime_cast/std_shared_ptr_cast.hpp